I would do the simplest thing possible. Which would probably be a report button that sends me an email and then I review it manually. With something social you

I would do the simplest thing possible. Which would probably be a report button that sends me an email and then I review it manually. With something social you need to be focusing your efforts on things that drive growth. If you spend a bunch of time building a robust moderation system, but nobody is using your app then it's wasted effort.